1. Field of the Invention
The invention relates to elongated perforating guns of the type generally used to perforate oil and gas wells, and particularly relates to a new design for a shaped charge carrier for such a perforating gun.
2. Description of the Prior Art
Perforating guns commonly used in wireline service operations for perforating an oil or gas well typically include an elongated cylindrical outer housing within which is received an elongated carrier which has a number of shaped charges in place in the carrier. The carrier is located relative to the housing so as to locate each of the shaped charges adjacent reduced thickness portions of the housing.
It is well known in the prior art to utilize either triangular or hexagonal cross-section tubular carriers constructed to receive three 120.degree. circumferentially spaced shaped charges in a given horizontal plane. When a hexagonal carrier is utilized, longitudinally adjacent layers of charges may be rotated 60.degree. relative to each other to spread out the pattern of perforations along the length of the well which is to be perforated.
Until relatively recently, the shaped charges have been held in place relative to the carrier by snap rings which interlock both with the outer case of the shaped charge and with the carrier, and by other separate attachment devices.
Recently the assignee of the present invention has developed an improved shaped charge carrier made of sheet metal which has openings formed therein along with resilient tab means adjacent those openings. The shaped charges may be assembled with the carrier by merely pressing them into the openings. The resilient tab means forcibly grip the shaped charges and hold them in place within the carrier.
This prior art device is shown and described in detail in U.S. patent application Ser. No. 651,201 filed Sept. 17, 1984, for SHAPED CHARGE CARRIER ASSEMBLY, which is assigned to the assignee of the present invention. The structure shown in FIGS. 1-7 and 13 of application Ser. No. 651,201 is a part of the prior art. That device utilizes a hexagonal cross-section tubular carrier for receiving the various shaped charges. It is noted that application Ser. No. 651,201 itself is not a part of the prior art. Applicants are merely referring to FIGS. 1-7 and 13 of that prior application as a convenient means of describing the structure shown in those figures, which structure is a part of the prior art. Any disclosure of application Ser. No. 651,201 which is not illustrated in FIGS. 1-7 and 13 is not conceded to be part of the prior art.
As is apparent from application Ser. No. 651,201, and particularly from FIG. 5 thereof, the construction of the hexagonal cross-section carrier is a rather complicated task, since that carrier is assembled from three sheet metal sections, each of which requires extensive forming work to manufacture. Additionally, substantial time and expense is involved in assembling the sheet metal sections to form the hexagonal cross-section carrier.